National Synchrotron Light Source II

1. National Synchrotron Light Source II Semi-permanent Setup at the NSLS for 0.1 meV Optics R&D Zhong Zhong

2. Acknowledgement Collaborators: Lonny Berman, Yong Cai, John Hill, Xianrong Huang, Yuri Shvyd’ko, and Peter Siddons Technical help: Scott Coburn, Shu Cheung, Richard Greene, Anthony Lenhard, Zhijian Yin, and Hui Zhong Expert advice: Alfred Baron, Michael Hart, Steve Hulbert, Chi-Chang Kao, and Francesco Sette, and many others

3. Why Bother? • A semi-permanent setup is attractive for serious experimentalists • 0.1 meV R&D will involve lots of trial-and-error … a local home base is preferred • Access may entice experts (such as Shvyd’ko, Alp, Baron) to come to BNL more often • A playground may entice local experts (Siddons, Berman, Kao to name a few) to roll up their sleeves, and play • Develops local expertise: one can only learn by doing, and making mistakes • Readily available x-ray is a NSLS-advantage, a luxury for APS, ESRF and Spring-8

4. The Approach • 0th-order approximation: Repeat the Shvyd’ko experiment (0.7 meV target) • Get to the end results as soon as we can, then work backwards • Small crystals will be used • It may be advantageous to have a CCD detector to watch the beam from day-one. The detector helps in understanding what really goes on in the crystals • Study and refine: surface quality? Crystal d-spacing uniformity? Crystal strain/mounting? Temperature uniformity and stability? Role of dispersion compensation? … • The list goes on, but the point is to get our hands dirty and start learning. • We hope to migrate/creep/leap: 0.7 meV -> 0.3 meV -> 0.1 meV

5. Feasibility • Involves direct beam, flux should not be a problem. • The angles involved are large (a few to 100 micro-radians) -> Vibration should not be a problem. • The divergence Shvyd’ko used is 15 micro-radians.  We can do that at the NSLS with 200-micron slit at 15 m.  • 200 micron in-plane -> 4 mm footprint on C, W crystals (b=20), and 4/tan(1.5)=120 mm on D crystal (1.5 deg offcut). Thus small crystals are sufficient. • Temperature stability is important but we can start with ambient and see what other problems we have.

6. Haves and Have-nots • What we have: • Access to X12A: NSLS R&D beamline on a bending magnet port • Control system, 111 channel cut monochromator • A CCD detector borrowed from X15A (10 micron pixel size, 30 x 40 mm2) • What we made: • Two asymmetric (88.5 deg) 008 D crystals • Two 220 CW crystals, with fancy 200-500 micron thin wafer • … Enough to keep us going for a while • What we (eventually) need • Temperature controlled crystal environment • Scanning diagnostic aperture in beam • A dedicated high resolution detector

7. CW (Collimator and Wavelength Selector) Crystal APS Design W C

8. NSLSII CW Channel-Cut Design lap 1.5 3/4 W 200-500 microns 3/8 3/8 400 2-20 1 C 19 deg 26 deg Weak link side-view 1/8 -2-20 040 Quantity: 2, cut 1.5x1x2, polish top, cut channels, slice into 2 crystals 004 W C 1 top-view

9. CW Tilt and W Tweak W 220 leaf spring, ½ mm thick 9.1315 keV C tth=41.4 deg, th=20.7 Tweak Epoxy Ball-bearing 2 picomotors 1.7 deg Tilt Newport tilt #39 http://www.newport.com/store/genproduct.aspx?id=144557&lang=1033&Section=Graphics

10. D Crystal (Dispersion Element) APS Design

11. NSLSII D Crystal Design 4 Top surface polished 1 400 1/8 400, 1.5 degrees offcut end- view 1/4 3/8 004 side-view 004 lattice planes 3/8 T shape to minimize weight and maximize stiffness 040 top-view 1 Quantity: 2, cut 4x2x3/8, polish top, slice into 2 crystals

12. Cutting from a 5-inch 004 boule 4 400 400, 1.5 degrees offcut 004 side-view 004 lattice planes 3/8 Radial cutting to minimize longitudinal d-spacing variation during crystal growth

13. Rough Cutting at the BNL Central Shop Abrasive Water Jet

14. Alignment at the NSLS

15. Aligned

16. CW Crystal NSLSII CW Crystal Before etching 0.4 mm 1 mm After etching Two blanks for future

17. Glued

18. Assembled in Beam 0.5 mm 1 mm After etching Two blanks for future Tilt Tweak

19. C Crystal Rocking Curve W C • Data is for 0.3x12 mm and 0.3x1 mm beams • Width (FWHM) is about 120 micro-radians, in agreement with expectations of 106 micro-radians • Monochromator energy was changed, and dE/E=dth/th was used to calibrate tilt motor

20. Beam Off CW Image plate 50 micron resolution Tuned By-passing W W Half-tuned 1 mm C Through W Detuned ¼ -tuned Imperfections mostly due to coating on Be window 12-mm wide

21. Rocking Curves Through W tuned ½ detuned C rocking curve, through tuned W W Rocking curve

22. W Transmissivity • Experiment w/ 0.2x1 mm beam • Simulation assumes 0.35 mm thick W • Excellent qualitative agreement • Peak Transmissivity is about 40%, in agreement with simulation of about 45%. • Measurement is consistent with 80% W intrinsic transmissivity.

23. NSLSII D crystal Glued Epoxy RTV Spare Leveling pin, removed later

24. In Beam

25. Poor-person’s Temp. Stabilization • Lights were turned off, and hutch door was closed overnight • Everything else stayed the same Before After 20 min. scan time

26. What Next? • Further characterization of D crystal • Verify the angular acceptance by mis-aligning the CDW assembly. • Design and build a second set of CDW assembly • CDW will be scanned against the second set to determine the energy resolution. • Depending on the resolution achieved, 0.3 or 0.1 meV version will be designed and tested.

27. Two Legs

28. Summary • NSLS bending magnet is suitable for 0.1 meV R&D. • CW Crystal performs as expected. Two such crystals in hand will be used for further development • Vibration control is appropriate (keeping it simple and stiff, minimize adjustments/weak links). • Free-standing thin-wafer concept provides good strain-relief for W crystal • Leaf-spring/weak-link mechanism provides fine adjustment

29. C Dumond Diagram

30. C Rocking Curve Simulation 111 pre-mono 220 intrinsic Convolved

31. CW Dumond Diagram < 5 micro-radians Beam through W

32. Detector Sheilding

33. CW Tilt and W Tweak